Field of the Invention
The invention relates to a swash-plate machine including a hollow spherical work chamber being divided by a partition into at least one high-pressure side and at least one low-pressure side, into which an operating medium can be conducted through a conduit system, the partition extending up to a piston carrier and cooperating with a plate-like sealing strip, a circular piston being adapted to the diameter of the work chamber and connected to the outside through a supported shaft effecting a tumbling motion of the piston, the piston having at least one piston slit extending radially from the circumference approximately to a piston carrier, and a guide journal being inserted into the slit and cooperating with the partition, the piston tapering outward toward the circumference, and the end surfaces of the piston being in contact with opposed lateral surfaces extending perpendicularly to the axis of rotation of the shaft and laterally defining the work chamber.
The invention relates to the field of swash-plate machines for pumping liquid and gaseous media, as a subcategory in the field of machines, particularly swash-plate pumps and swash-plate compressors.
One such swash-plate machine has been disclosed by German Published, Non-Prosecuted Application DE 35 42 648 A1. The teaching of that application relates to a swash-plate machine with a circular-annular piston disposed in a hollow-spherical work chamber. The piston is retained in a piston carrier and is set into tumbling motion by a drive shaft. The piston carrier, which is acted upon directly by the shaft, is in positive engagement with the piston and imposes the tumbling motion upon it. The partial work chambers located on both sides of the piston, which are formed by a partition in engagement with the piston, function as a high-pressure and low-pressure chamber, depending on the direction of rotation of the drive shaft that drives the piston carrier, and the applicable medium is delivered to and removed from those chambers.
In the case of high-viscosity media, such as molasses or heavy oil, tightness is adequately assured, with only moderate friction. However, with low-viscosity media, leaks and increased wear can arise from unavoidable friction between the piston guide and the partition.
The piston guide in that case includes a guide journal inserted into a radial slit made in the piston. In its basic form, the journal is constructed as a circular cylindrical column with a slit. The slit corresponds to the wall thickness of the partition and is engaged by the partition. In accordance with the tumbling motion of the piston produced by the piston carrier set into rotation by the drive shaft, the guide journal slides along the partition.
A provision for overcoming that disadvantage which is often employed in such cases, namely to reduce the dimensional tolerances in the known machine, particularly of the parts that move relative to one another, with one example being the width of the slit in the guide journal, has proved impracticable. Reducing the dimensional tolerances can in fact cause increased wear or even machine failure, for instance from welding resulting from excessive friction, and is therefore not an option.